This invention relates to a pneumatic weighing device and method, and more particularly to a weighing device capable of receiving articles to be weighed at high speeds.
In many manufacturing process, especially in the canning industry, quantity control is a very important parameter. To achieve efficiency in the weighing function in any canning process, for example, it is necessary to eliminate manual weighing of the individual articles. Automatic high speed weighing systems are utilized to move large quantities of product over a conventional scale to separate the product falling outside a predetermined weight range.
In some high speed weighing systems conveyor belts are used to transport products. The conveying system transports the product to a weigh conveyor having a lightweight belt material, or an endless chain system, and operating in a fashion to move over a conventional scale. Thus, when a product is transferred to the lightweight conveyor the weight of that product will be determined as it moves over the scale.
Since a conventional scale having either torsion or compression springs are utilized in these systems many disadvantages result. For example, there is a required damping time or settling time after each individual product is weighed. Since there must be an interruption in time between weighing individual products, a further problem of spacing the objects to be weighed is encountered. By moving a conveyor belt over the scale there is also mechanical vibration to overcome. Although dash-pots and other damping elements have been used to solve many of these problems, spring loaded scales tend to either overact or counteract. Also, since the product to be weighed is being transported over a conventional spring loaded scale, lightweight belts are necessary on the conveyor to eliminate added weight on the scale. Repeated use of these lightweight belts will yield to mechanical wear and increase the cost of operation of the weighing process.
Thus, the major disadvantage in existing weighing devices utilized for high speed weighing is in the interdependence of the transport mechanism and the weighing mechanism.